Bovine respiratory disease

Pneumonia accounts for 22.5% of all deaths in pre-weaned calves, second only to scours as the leading cause of mortality. Most of the costs associated with pneumonia are the result of reduced liveweight gain and feed conversion efficiency. These in turn result in losses through increased finishing times, increased feed costs and increased age at first calving. Pneumonia is a massive source of inefficiency and may contribute substantially to a farm’s antibiotic usage and carbon footprint.

Now is the time to critically appraise your buildings and management policies and ask yourself the question, what changes could be made to reduce the risk of respiratory disease?

The incidence of pneumonia increases by 43% in cattle sharing air space with a persistently infected BVD animal.

Optimal colostrum management – Calves should receive 10% of their bodyweight in good quality colostrum (>55g/l) within 6 hours of birth (preferably within 2 hours). Colostrum and transitional milk feeding should continue for 4-5 days.

Optimal nutrition throughout the pre- and post-weaning periods – ensure the diet contains sufficient energy for growth and a functioning immune system. Choose a good quality milk replacer and feed at the correct concentration, volume, and temperature (feed at 37-39°C). Provide a good quality concentrate, age-appropriate forage, and fresh clean water. Feeding practices should be adapted to meet the additional nutritional needs of calves during cold weather spells. For example, for every 5°C drop in temperature below 15°C feed an additional 50g of milk replacer (or 0.33l of whole milk) per day. If this amount increases the total volume of milk significantly it is better to split the feeds into three, rather than two large feeds. Although this requires extra labour, maintaining growth rates and immunity through cold weather periods definitely pays off.

Provide adequate ventilation whilst minimising draughts – Building design should support a constant source of fresh air coming in and allow continual escape of stale air. Air movement at calf height should be <0.3m/sec. Measure air speed at multiple points in the shed at calf height and use smoke pellets to observe how quickly air is dissipated. Air flow should be uniform, and draughts should be avoided. Use solid barriers at calf height and fill in the gaps under doors and partitions. A positive pressure tube ventilation system will ensure that clean air is delivered, whatever the external weather conditions. Using a fan without a tube is not a good idea as air delivery is not equal throughout the building.  In some cases, small and relatively inexpensive alterations can have a very positive impact on calf health.

Ensure good drainage to reduce humidity – High humidity in buildings reduces the temperature felt by the stock and increases pathogen survival. Control of moisture in calf houses is essential and requires good drainage and effective ventilation. There should be no standing water in calf sheds; all floors should be kept dry.

Improve air quality – Reduce dust and ammonia levels which damage the natural defence mechanisms of the respiratory tract. Avoid calves sharing the same air space as older cattle.

Provide adequate bedding – In cold weather calves should have sufficient bedding to allow them to “nest”. Nesting can be graded on a scale of 1-3, with 3 being legs fully covered when lying down – warm and toastie! Calves less than 3 weeks of age will benefit from a jacket if the temperature drops below 15°C. Calf jackets are recommended for calves older than 3 weeks at temperatures below 5°C.

Vaccination – It is important to diagnose which pathogens are present so that vaccination policies can be tailored to the individual farm.

Eradicate BVD – Have a policy in place to ensure there are no persistently infected (PI) BVD animals on farm, as these cattle are a constant source of infection and cause immunosuppression across the whole group. Tag testing is the most efficient and cost-effective way to do this.